The country's first issue of debt in two years has added to its positive momentum, rating agency Fitch said.
But it remains unclear how much access to bond markets it will have once its EU/IMF bailout expires at the end of next year, it warns.
The NTMA last month issued €4.2 billion of medium-term bonds, the first time a country in a euro zone bailout programme has done so.
"The recent financing measures have added to Ireland's positive credit momentum (and) improves its chances of making a full return to the bond markets later this year," Fitch said.
"However, market confidence remains extremely fragile, and a further escalation of the euro zone crisis could thwart the sovereign's return to the capital markets," it cautioned.
Plans to issue between €3 billion and €5 billion of sovereign annuity bonds for the first time, "underlines the sovereign's improving financing flexibility," the agency said.
Even if Ireland fails to return fully to markets, bondholders are unlikely to be compelled to take write-downs on their Irish sovereign debt holdings, the agency said. Private bondholders were required to take a hit on Greek debt, but that has since been declared a one-off by those negotiating EU/IMF bailouts.
Fitch has a BBB+ rating with a negative outlook on Ireland. It said this reflects the country's large fiscal deficit and its susceptibility to contagion from an intensification of the euro zone debt crisis that could cut demand for Irish debt.